Lab 7 - Cell Division: Mitosis and Meiosis

Finished lab report is in Google Drive. Don't look here.

Hey! I said don't look.

1. How do eukaryotic cells divide to produce genetically identical cells or to produce gametes with half the normal DNA?


2. Pre-lab Questions:

1. How did you develop from a single-celled zygote to an organism with trillions of cells? How many mitotic cell divisions would it take for one zygote to grow into an organism with 100 trillion cells?

The zygote divides over and over until a blastocyst is formed. This blastocyst is composed of many stem cells which then specialize into the many different types of cells found in an organism. These specialized cells then divide and come together to form tissue. This tissue then comes together to form organs. These organs come together to make baby. It would take 10 million mitotic cell divisions to make an organism with 100 trillion cells.

2. How is cell division important to a single-celled organism?

Cell division is important to a single celled organisms because it allows the organism to make more of its kind so the species does not die out.

3. What must happen to ensure successful cell division?

The chromosomes must be replicated so that each daughter cell would come out of the division as 2n cells. First mitosis occurs, which is when the nucleus splits and the two new nucleuses for the two 2n daughter cells is created. Then in cytokineses, the cell membrane is split into two new daughter cells that contain the necessary organelles. If meiosis is the process that is occurring then the two daughter cells would split again into four n cells.

4. How does the genetic information in one of your body cells compare to that found in other body cells?

The genetic information found in each body cell is the same; the only difference between them is what is being expressed.

5. What are some advantages of asexual reproduction in plants?

If a plant can't find another plant to sexually reproduce with then the only way the species can continue existing in that location would be with asexual reproduction.

Also if a plant has an advantageous trait then there is a much higher probability the offspring will inherit that trait with asexual reproduction than sexual reproduction. This would then help the species continue existing as long as the environment is stable.

6. Why is it important for DNA to be replicated prior to cell division?

If the DNA is not replicated before the cell divides then the daughter cells will only have half the necessary chromosomes and genetic code; it would be n rather than 2n if mitosis is the process that occurred.

7. How do chromosomes move inside a cell during cell division?

The spindle fibers during mitosis attach to the centromeres of the chromosomes which are in the center. The splitting of the nucleus causes half the chromosomes to go in each new nucleus that is formed.

8. How is the cell cycle controlled? What would happen if the control were defective?

It is controlled by cyclins and CDKs. When these accumulate over time and eventually reach a certain number, the cell advances to the next stage. Cyclins attach to the CDKs which then allows the CDKs to do something to make the cell advance to the next stage, such as breaking down the nucleus. If this control of the cell cycle was defective then the cell might move on to the next stage when it is not ready which could cause problems later on in the cycle or for the daughter cells.

3. How is cell division controlled?

There are checkpoints which use cyclins and CDKs through out the cell cycle where the amounts of these chemicals and proteins determine if the cell is ready for the next stage and allows it to continue. If something is wrong then the cycle is halted and a correction is made. If a correction can't be made then apoptosis occurs in the cell.

Explain how eukaroytic cells divide to produce genetically identical cells.

The chromosomes of the cell are replicated so there are double the regular amount of sets of chromosomes in the cell making it a 2n cell. The sister chromatids of a chromosome are connected by the centromere. During mitosis spindle fibers attach to the centromere and help sort out the DNA to make sure the daughter cells have the correct amount of chromosomes when cytokineses occurs and the membrane is split to make two cells.

If a cell contains a set of duplicated chromosomes, does it contain any more genetic information than the cell before the chromosomes were duplicated?

The genetic information still codes for the same stuff as the cell before the chromosomes were duplicated.

What is the significance of the fact that chromosomes condense before they are moved?

It is to make sure that sister chromatids do not end up in the same daughter cell. The sister chromatids attach and then are all detached at the same time before the nucleus is split to insure that nothing goes wrong with the chromatid counts in the daughter cells.

How are the chromosome copies, called sister chromatids, separated from each other?

Before the nucleus is split the sister chromatids are connected by their centromeres and the spindle fibers in mitosis pulls them apart.

What would happen if the sister chromatids failed to separate?

If they failed to separate then one of the daughter cells would have an extra chromatid and the other daughter cell would be missing a chromatid. Not really good news for the cell's survival.

Hypothesis: If lectins are introduced to a plant, then the root tips of the plant will grow because of an increased mitotic rate.

Null Hypothesis: If lectins are introduced to a plant then nothing will happen


  1. Cut up a little slices of root tip cells. Place these slices under a microscope and count and record how many cells you see.
  2. Introduce varying amounts of lectins to each of the samples and wait a day. Make sure to have one sample that is not introduced to the lectins and to record the varying amounts of lectins you place in the each sample.
  3. Count the new amount of cells in each sample and record.
  4. Analyze the data to see if the cell counts in the samples increased and by how much.

Pg. S90

What was the importance of collecting the class data?

A large sample size helps make our results more accurate.

Was there a significant difference between the groups?


Did the fungal pathogen lectin increase the number of root tip cells in mitosis?


What other experiments should you perform to verify your findings?

Test to see how varying amounts of lectin affect the amount of root tip cells in mitosis.

Does an increased number of cells in mitosis mean that these cells are dividing faster than the cells in the roots with lower number of cells in mitosis?

If more cells are in mitosis that that would mean that more cells finished up with interphase and started mitosis so the cells would be dividing at a higher rate.

What other way could you determine how fast the rate of mitosis is occurring in root tips?

You could put one sample in lectins and another in water and come back a couple days later and weigh the samples to find the difference (I don't know).

Comment Stream

2 years ago

Please delete your tackk, thanks